Method of manufacturing progressive burning molded nitrocellulose gun powder



Sept. 19, 1961 H. J. L. DONKER 3,000,721

METHOD OF MANUFACTURING PROGRESSIVE BURNING MOLDED NITROCELLULOSE GUN POWDER Filed June 13, 1960 3 Sheets-Sheet 1 A/G 70500? 645/6 (HA/96A /55 //w 30 d/ /Pm) 0 g B O ZBY Wi/GHT 1 Sept. 19, 1961 H. J. DONKER 3,000,721

METHOD OF MANUFACTURING PROGRESSIVE BURNING MOLDED NITROCELLULOSE GUN POWDER Filed June 13, 1960 v 5 Sheets-Sheet 2 Cl/EV'S REPRESENT AVERAGE VALUES OF 3 7ZLLY/IV6 IA/flEPE/VDE/VT 50MB 75975 BOMB 700 CC. 4= 0.2

20% 40% 60% 50% max sue/v7 FGACT/O/V Sept. 19, 1961 H. J. DONKER 3,000,721

METHOD OF MANUFACTURING PROGRESSIVE BURNING MOLDED NITROCELLULOSE GUN POWDER United States Patent 3,000,721 METHOD OF MANUFACTURING PROGRESSIVE BURNING MOLDED NITROCELLULOSE GUN POWDER Hendrik Jean Louis Donker, Muiden, Netherlands Filed June 13, 1960, Ser. No. 35,524 Claims. (CI. 52-20) This invention relates to methods of preparing nitrocellulose gun powder having progressive burning characteristics. This application is a continuation-in-part of application Serial No. 616,842 filed October 18, 1956, now abandoned.

An object of the invention is to provide improved methods of providing progressive burning characteristics.

Another object of the invention is to provide methods whereby the calorific values can be precisely determined for the outside of gun powder particles and whereby the gradient of said values towards the inside of the particles can be selected substantially as desired with powder particles of any dimensions ballistically necessary.

According to the invention, there is contemplated a method of imparting progressive burning properties to a molded nitrocellulose powder by immersing said powder in a solution of ethanol containing 20 to 0% of water by volume and a percentage of a phlegmatizing agent at a predetermined temperature. The percentage of said agent is adapted for giving at said temperature, in equilibrium with said powder, a powder with a positive determinable apparent heat of combustion. The period of time of immersing is adapted to a determinable percentage of the weight of'the powder to be absorbed of said agent by said powder, which period of time depends on said temperature, said composition of the solution and the dimensions and composition of said powder. Subsequently, the ethanol is eliminated from the product obtained.

Further objects as well as features and advantages of the invention will be found in the following detailed description as illustrated in the accompanying drawing in which:

FIG. 1 is a graph illustrating burning characteristics of a neutral powder;

FIG. 2 is a graph comparing different burning characteristics;

FIG. 3 is a graph showing the penetration into molded powder of ethanol and phlegmatizing agents as a function of time; and

FIG. 4 is a graph illustrating equilibrium conditions according to the invention.

In the generation of pressure in the closed bomb calorimeter, if z is the fraction of the amount of powder burnt in time t, the following equation holds good:

in which to is the original weight and w, the weight at time t;

is the rate of combustion of the mass.

If the linear rate of combustion is expressed in the in which S represents the surface area at time t and S the-original surface area;

6 represents the density and W represents the original volume of the powder. 1 I

v v 3 .4 o represents the change of the surface area during the combustion. Said change is a function of z. It is called the function of form ;f(z)

is the effective wall thickness.

is called the vivacity.

As regards homogeneous gun powder, the vivacity A is supposed to be a constant inasmuch as the linear rate of combustion at a given pressure is approximately constant.

There are indications to the etfect that the linear rate of combustion slightly increases inwardly which may be explained, because nitrocellulose (N.C.)-molecules are more directed according to the longitudinal axis of the direction of compression at the outside than at the inside, while the linear rate of combustion is supposed to be larger in the longitudinal direction of the molecules than in transverse direction. This phenomenon has been investigated and if it is present at all the eifect is very weak and does not find expression in the bomb calorimeter in the case of NC. powder in tubular form and of homogeneous composition. Let it be supposed, therefore, that A is constant (for a homogeneous paste).

is to increase to a greater extent than according to the pressure factor pa, f(z) will have to increase, therefore, during the progression of the combustion.

Powder satisfying the equation ](z) 1 is called progressive powder,

powder satisfying the equation f(z)=1 is called neutral powder and powder satisfying the equation f(z) 1 is called digressive powder.

If it is now supposed that:

A=constant thentheequation dz AP holds goods.

Furthermore except for a few minor correctionsespecially as regards the change in co-volume-the following equation holds good as regards the combustion of said powder in a closed vessel z=P/ Pm (4) in which Pm is the maximum pressure.

Then:

d (P/ Pm) dt ---T,- A

The curve d (P/ Pm) dt will be a horizontal straight line. The surface area of powder of the single perforated cylinder type will slightly decrease upon combustion. The above curve will have to decline homewhat in said case, because in Formula 5 A will have to be replaced by Af(z).

If on the other hand aa l then the equation d(P/Pm) dt P holds good.

Notwithstanding the fact that (z)=l, the curve may all the same incline in upward or downward direction owing to oa 1. The inclination in upward direction of the curve owing to this fact is further left out of consideration, because in said case a would have to be essentially larger than 1. In his book: Theory of Interior Ballistics of Guns, pages 40 and 71, Corner writes about this matter:

Among production propellants, the highest a recorded has been 1.02.

The values accepted now for normal propellants are at gun pressures, between 0.9 and unity.

One on of 1.02 is so little above unity that the ditference is not significant. Values of on between 0.8 and 0.9 were obtained in early lots of certain propellants. With increased experience in their production a rose to 0.9.

After the corrections mentioned under (4), especially for covolume, a horizontal line must therefore be found for the function d (P/ Pm) dt in the case of tubular powder if m=l. FIG. 1 of the drawing shows that this is the case as a matter of fact. Said powder, therefore, is about neutral. Powder of the single perforated cylinder type is weakly digressive if a=l and flake type powderis more strongly digressive, whereas powder of the multi(7)perforated cylinder type (as regards its function of form) should have to be progressive. The fact that there is little to show this, is beyond the scope of this introduction.

Hereinbefore, therefore, there has been considered the concepts:

Neutral burning digressive burning and progressive burning powder as a result of the function of form f(z) for powder having a homogeneous composition, so A=constant. Another theoretical possibility of obtaining a progressive burning powder is to realize a progressivity in A.

If it is supposed that al, while as regards the function of form the powder is neutral or Weakly digressive, it will be clear that for said portion of the curve d(P Pm) plotted against P/Pm which rises instead of being horizontal the powder is at any rate progressive burning as a result of a progressivity in the paste.

Seeing that the a of nitrocellulose powder is smaller than 1, the ordinary curves of nitrocellulose powder of homogeneous composition having a substantially neutral function of form slowly decline (declining towards the x axis). A comparison of the d (P/ Pm) dt curve of an untreated homogeneous powder which afterwards is made progressive by the treatment according to the invention then shows in a correct and convincing manner the degree of progressivity as a result of the composition of the paste (see FIG. 2).

It will be clear that in order to realize progressivity in the linear vivacity as a function of z a type of powder is to be strived after in which owing to a difference in chemical composition the rate of combustion increases from the exterior towards the interior of the grains.

Powders of diiferent calorific values (so of a different A) have been rolled together without a satisfactory result being obtained, this being due to a poor reproducibility and a discontinuous change in vivacity of the product.

Fauveau and Chosson in Memorial des Poudres 1953, page 175 etc. describe an impregnating process with phlegmatizing agents (agents reducing the vivacity) in liquid. They also call this precipitation progressive." It is applied to a spherical powder, containing 10-15% of nitroglycerol (N.G.).

As a solvent a dilute aqueous ethanol of about 2l /2% by volume of ethanol is used. The absorption of ethanol by the powder is neglected and in all probability hardly takes place. The nitroglycerol is the vehicle. The absorption times are very short. The process cannot be successfully applied to nitrocellulose powder (N.G.- powder).

Also powder, especially for small weapons of slight dimensions (wall thickness less than 0.5 mm.) has been subjected to an impregnating process with phlegmatizing agents in a rotation drum and the result obtained was ballistically favorable. However, only a very thin layer is impregnated here into which layer the phlegmatizing agents have penetrated in a rather high concentration, which penetration, moreover, cannot be reproducibly controlled. As it is concentrated solutions in, for example, ethanol are used here, which in relatively small amounts relative to the powder to be treated are added to said powder in a rotating drum. If the powder gets too wet it will not roll in the drum. The alcohol will evaporate and a fresh amount of the solution is to be added again. The effect remains very superficial (i.e., it remains limited to a thin outer layer), neither the concentration of the phlegmatizing agents in the surface layer nor the depth of the penetration being controllable.

For small Weapons the ballistic result is fairly satisfactory, though susceptible of improvement, for larger weapons (larger wall thickness) the result, however, was decidedly unsatisfactory. Naturally this process is confined to powder which will roll in the drum and the longitudinal dimension of which, therefore, is limited relative to the other dimensions, such as flake or perforated cylinder type powder (single or multiple perforated).

Normally, this treatment is continued until the amount of phlegmatizing agent added amounts to some percentages of the weight of the powder. As an example may serve a rifle powder dimensioned 1.3x1.3x0.25 mm. and having an initial apparent heat of combustion (aHC) of 930 cal., which for each hundred parts by weight of powder has absorbed 2 /2 parts by weight of diethyldiphenylurea (diethylcentralite) during the treatment. The aver age aHC of the powder will have decreased to about 856 cal. then after the treatment. It is supposed that the centralite is absorbed by the outer layers to a weight of /s of the total grain weight and that no centralite has penetrated to beyond said outer layers, which about corresponds with reality. Said outer layers then have absorbed about 12.5% by weight of centralite. The aHC of said outermost /s portion has become about 600 cal. then on an average. If new a same percentage of centralite were absorbed by powder which per unit of Weight only has /3 or A of the surface area and if absorption were limited to a layer of the same thickness the centralite would be absorbed by about or of the total weight of the powder and said portion would contain then 37 /2% and 50% respectively of centralite on an average. The aHC of said layer would amount to about calories in the first case thenand in the second case it would be negative; i.e. said layer would not be capable of burning then without the addition of oxygen.

The fact that this situation about corresponds with actual practice does appear from an investigation of a foreign powder treated in such a manner and meant for a caliber larger than 20 mm., having a thickness of about 0.65. mm., in which for the outermost 0.01 mm. of the powder a negative aHC was found as a matter of fact, while it appeared that the phlegmatizing agent had penetrated less than 0.04 mm. (see FIG. 2; dot-dash line).

It will be clear that the method described hereinbefore will less and less lead to a really progressive burning powder as the wall thickness of the grains of powder increases. The maximum thickness of the grains of powder at which thickness this method will yield results that are still usable to some extent is in the neighborhood of 0.5 mm.

It has also been found that with this method it is not possible to control accurately the degree of penetration into the grain, because neither the temperature nor the amount of solvent which is withdrawn from the process by evaporation can be controlled. Furthermore, it is necessary to limit the amount of solvent, because otherwise the powder will no longer roll in the drum. Now I have found a method of manufacturing a progressive burning molded nitrocellulose powder which resides in impregnating the powder with a solution of one or more phlegmatizing agents, which method may be applied to powder grains having a thickness upwards of 0.5 mm., while it also has advantages if applied to powder grains having a thickness smaller than 0.5 mm.

The method according to the invention is based on the discovery that by immersing a molded nitrocellulose powder at a determinable temperature long enough in a solution of varying quantities of a phlegmatizing agent in alcohol with a definite water vcontent corresponding to each determinable concentration of the phlegmatizing agent, an equilibrium arises between said solution and the powder, whereby the powder absorbs a determinable quantity of alcohol and of the phlegmatizing agent. After eliminating the alcohol by drying, a powder results with (for each concentration of phlegmatizing agent in the solution at said temperature) a corresponding definite composition, whereby the powder through and through has absorbed a definite quantity of phlegmatizing agent and reached a corresponding definite calorific value. The magnitude of this equilibrium calorific value depends on the concentration and the nature of the phlegmatizing agent in the alcoholic solution, the percentage of water which the alcohol contains, the temperature and the composition of the nitrocellulose used. Within large limits of calorific values, powders immersed in said solutions for a sufliciently long period of time are, as regards physical and ballistic properties, practically identical to powders originally mixed to give corresponding calorific values.

FIG. 4 shows the apparent calorific values empirically determined for a nitrocellulose gun powder (composition of 100 parts by weight of nitrocellulose with 13.15% N content, 1 part by weight of diphenylamine) in equilib- -rium with the solution of the phlegmatizing agents listed on the graph, at 30 C., 37.5 C. and 45 C. after the 'gun powder is dried.

For instance, point A represents the apparent calorific value after immersing the original powder in a solution of 100 parts of alcohol containing 91.5% of ethanol by volume and 8.5% of water by volume to which has been added 10.3 parts of diamylphthalate by weight, 4.12 parts of diethylcentralite by weight and 2.5 parts of diphenylamine by weight at 375 C. until equilibrium and drying the powder. This apparent calorific value is 400 calories.

Point B gives in the same way using a liquid consisting of 100 parts of alcohol containing 91.5% of ethanol by volume to which has been added 8.4 parts of diamylphthalate by weight, 3.32 parts of diethylcentralite by weight, and 2.5 parts of diphenylamine by Weight in equilibrium at 45 C. a propellant having an apparent calorific value of 605 calories.

With other phlegmatizing agents similar equilibriums exist and can be empirically determined.

As the original powder normally contains 1% of diphenylamine and the content of diphenylamine in the powder should be unchanged, in the solution wherein the powder is immersed a concentration of i- 2 /z% of diphenylamine is needed as diphenylamine is not absorbed very selectively by nitrocellulose.

To manufacture a powder with progressive burning properties from a molded powder according to the invention an alcoholic solution is prepared from alcohol with a water content by volume of 20-0% water and a definite quantity of phlegmatizing agent by weight in parts of the watery alcohol by weight, said quantity being the quantity corresponding to the determined temperature that will be used for the immersing process to a desired equilibrium calorific value.

In said solution, the powder is immersed at said temperature for a determinable period of time as explained hereinafter. The outside layers at the surface of the powder particles will rapidly assume a composition corresponding to the equilibrium calorific value belonging to the said conditions and will stay at that value. The alcohol and the phlegmatizing agent continues to penetrate to the inside of the powder particles during the immersion. After a determinable time the desired quantity of phlegmatizing agent has been absorbed. This may be, for instance, when /3 of the quantity belonging to the equilibrium conditions has been absorbed. The powder is then taken out of the solution, freed from the major portions of the adhering solution by washing, and dried. The time depends on the working temperature, the composition of the solution and the composition and the dimensions of the powder particles and is determined experimentally. In this manner, no part of the powder particles can ever get a calorific value that is lower than the calorific value of the corresponding equilibrium situation.

The outside layers near the surface of the powder particles receive about the equilibrium calorific value, while more to the inside of the particle the calorific value mounts up gradually to the original value of the powder, while the very inside of the particle keeps its original composition and calorific value. The longer the impregnating time is chosen, the smaller this part of unchanged calorific value will be.

The ballistic problem that has to be solved determines the desired calorific value which the outside layers of the powder particles should receive and therefore the composition of the solution to be used for immersing the powder as well as the extent by which the phlegmatizing agent should be allowed to penetrate the particle and therefore the quantity of absorbed phlegmatizing agent.

However, the same gradient in burning properties can be achieved for powders of different and substantially unlimited web size, while the immersing time is almost proportional to the square of the web size under comparative conditions.

It should be noted that the molded powder rendered progressively burning according to the invention may undergo an after-treatment, for example, in order to glaze it, in which case the outer layer may obtain a negative apparent heat of combustion.

The phlegmatizing agents should be sufficiently soluble in the solvent and the solvent must be absorbed by the nitrocellulose to a sufiicient extent in order to serve as a vehicle for the phlegmatizing agents. Seeing that benzene does not come up to the last-named requirement it cannot, for example, serve as an impregnating liquid. Polar solvents, notably the lower alcohols, such as methaoobjai 'anol, ethanol, 2-propanol and the higher alcohols, provided that they are mixed with a suflicient amount of methanol or ethanol, are suitable for the purpose.

The phlegmatizing agents on the other hand should have enough absorbing aflinity to the nitrocellulose to attain a sufliciently low equilibrium calorific value. The normally used phlegmatizing agents for surface treatment of nitrocellulose powders all fulfill that condition.

A suitable solution for impregnating the powder is, for example, an ethanolic solution to which per 100 parts by weight of aqueous ethanol (92.5% by volume of ethanol) 10.5 parts by weight of diamylphthalate, 4.25 parts by weight of diethylcentralite and 4.5 parts by weight of diphenylamine have been added. With a duration of the impregnation of about 36 hours at 37.5 C. this liquid will give an aHC in the outer layer of about 350 cal. and at 50 C. of about 500 cal.; the aHC of the original powder is 800-950 cal. A stronger or a weaker solution will respectively produce lower and higher values. An increase in temperature will increase the rate of absorption of the phlegmatizing agents, but will give higher aHC equilibrium values owing to the smaller afiinity of phlegmatizing agents to nitrocellulose at elevated temperatures.

The localization of the penetrated phlegmatizing agent was determined by carefully dissolving the powder stepwise in dilute alcoholic potassium hydroxide, carefully stripping the remaining non-dissolved portion from re agents, drying it and determining the aHC. A comparison of powders follows:

A. Conventional powder, single perforated cylinder having a thickness of about 0.65 mm., aHC dry 784 cal.

Removed 3.45% by weight, aHC of the remaining portion: 851 cal.

Calculated aHC of removed portion 109l cal.

(minus 1091 cal.).

Removed 6.5% by weight; aHC of remaining portion:

865 cal.

Calculated aHC of removed portion between 3.45

and 6.5%: 422 cal.

Removed 11.8% by weight, aHC of remaining portion: 866 cal.

Removed 18.1% by weight, aHC of remaining portion: 866 cal.

Removed 39.4% by weight, aHC of remaining portion: 866 cal.

B. Powder impregnated according to the invention, dimensions 7 x 7 x 0.93 mm., aHC prior to the impregnation 945 cal. (dry), after the impregnation aHC 816 cal. (dry).

a. The outer layer was removed up to 7% of the weight of the powder; aHC of the dried remaining portion 842 cal.

Calculated aHC of the removed portion: 442 cal.

b. The outer layer was removed up to 12.2% of the weight of the powder; aHC of the remaining portion 853 cal.

Calculated aHC of removed portion between 7 and '0. The outer layer was removed up to 23.9% of the weight of the powder; aHC of the remaining portion: 885 cal.

Calculated aHC of removed portion between 12.2 and 23.9%: 645 cal.

21. The outer layer was removed up to 44% of the weight of the powder, aHC of the remaining portion: 914 cal.

Calculated aHC of removed portion between 23.9

and 44%: 813 cal.

e. The outer layer was removed up to 65% of the weight of the powder; aHC of the remaining portion: 941 cal.

Calculated aHC of removed portion between 44 and 65%: 857 cal.

out as follows:

The powder freed from the major portion of the sol vent in vacuum driers at about 65 C. is introduced into a hopper-shaped heat insulated vessel having a perforated bottom. Said vessel is filled with the impregnating liquid of a specific composition and temperature up to the overflow with which the apparatus is equipped, in such a manner that the powder is entirely submerged. The impregnating liquid of controlled temperature and of a composition which is kept constant is pumped into the vessel from the bottom upwards and will flow over at the top.

In order to promote the swelling and the uniformity of the impregnation an agitation is regularly applied by blowing in air of such a pressure that the mass is temporarily fluidized. After the desired duration of the impregnation has been reached, the impregnating liquid is drained and according to requirements the powder is freed from the adhering impregnating liquid by washing and it is freed from the major portion of the solvent in vacuum driers at about 65 C. to be subsequently humidi fied in the conventional manner. If desired the powder may subsequently or prior to the humidification be subjected to a conventional surface treatmentin the main by means of graphite or tin powder in a rotating drum in order to increase the specific volume.

After the vacuum drying the impregnation may be repeated in the same liquid and at the same temperature or in another liquid and at another temperature in order to increase the progressive effect. This is due to the fact that during the absorption the alcohol will penetrate the powder first.

The impregnating process should be terminated before too large an absorption of alcohol would render the grains too pervious to the impregnating agent. If it is all the same desired then to cause the powder to absorb a greater portion of phlegmatizing agent the alcohol should first be removed by drying in vacuum and the impregnation should only then be repeated.

The course of the absorption of alcohol and phlegmatizing agent from an ethanolic solution of phlegmatizing agent by strip powder is shown in principle in FIG. 3 and the sharp bends of the absorption lines show almost the point where the powder becomes too pervious to the impregnating agent.

The absolute height of the curves is dependent on the temperature and the concentrations, the time is dependent on the temperature.

Besides from the localization of the penetrated impregnating agent as described hereinbefore the difference in progressive efiect appears from a comparison of the course of the vivacity (the function 5/ P.Pm,,,--P/P (1) Convenventional powder treated according to the old method,

(2) untreated powder,

(3) the same powder after it has been subjected to the method according to the invention (see FIG. 2).

The advantages of the progressive linear vivacity in ballistic respect have been confirmed by experiments. They appear from the comparative pressure-time diagrams in the weapon.

The powder manufactured according to the invention when tested in the cannon shows a surprisingly small erosion owing to the initially relative cold gases evolved which remain relatively cold for a long time, while retaining their good ballistic properties.

EXAMPLE I A molded nitrocellulose powder of the single perforated cylinder type having the composition containing 13.2%

of N, to which per 1000 parts by weight of dry matter have been added: 1 part by weight of a flame damping salt (potassium bitartrate), 1% parts by weight of diphenylamide and 1% parts by weight of diethylcentralite is forced through a die having a diameter of 3.30 mm. and over a mandrel having a diameter of 0.60 mm., so that a powder results having a wall thickness of about 0.85 mm. (external diameter about 2.20 mm., internal diameter about 0.50 mm.) and cut to a length of 8 mm. to form grains of the single perforated cylinder shape. After removal of the solvent a powder will be obtained having an aHC of about 930 cal.

In a vacuum drier said powder is freed from the solvent at about 65 C. until only about 2% of said solvent is left and it is impregnated in an impregnating hopper for 36 hours at 37.5 C. with a 95% by volume ethanol, to which per 100 parts by weight have been added:

2.5 parts by weight of diphenylamine 9.5 parts by weight of diamylphthalate and 4.5 parts by weight of diethylcentralite.

Subsequently the impregnating process is terminated, the liquid is drained and the powder is washed two times with cold ethanol, which at most contains some impregnating liquid originating from the previous washing treatment and immediately thereafter the ethanol absorbed is removed for the larger part in a vacuum drier at 65-70 C., 'which' requires about 12 hours (residual ethanol about 2%). Subsequently the powder is glazed in the glazing drum for which purpose may be used:

0.1% of graphite 0.4% of tin powder 3% of ethanol to be subsequently freed from the residual solvent in the conventional manner by a hot water treatment and to be dried.

The impregnated product has an aHC of about 780 cal., the exterior has an aHC of about 400 cal., the interior has an unchanged aHC of about 930 cal.

10.5 parts by weight of diamylphthalate 4.25 parts by weight of diethylcentralite 2.5 parts by weight of diphenylamine 31 hours at 37.5 C.

aHC 775 cal.

aHC of the outermost portion about 350 cal.

EXAMPLE IH Powder As in Example H.

Liquid 100 parts by weight of ethanol (91.5% by volume), to which have been added:

8 parts by weight of diamylphthalate 3.25 parts by weight of centralite 2.5 parts by weight of diphenylamine.

Result 40 hours at 37.5 C., aHC 770 cal. (without an aftertreatment in the drum).

aHC of the outermost portion about 480 cal.

10 EXAMPLE IV Powder As in Example II.

Liquid 100 parts by weight of ethanol (91.5% by volume) to which have been added:

12 parts by weight of diamylphthalate 5 parts by weight of centralite 2.5 parts by weight of diphenylamine.

Result After 23 hours at a temperature of 40 C.-aHC 765 cal aHC of the outermost portion about 295 cal.

EXAMPLE V A molded nitrocellulose powder, 13.2% N, to which per 100 parts by weight of dry matter has been added:

1 part by weight of diphenylamine 1 part by weight of flame damping salt aHC 955 cal., 3/0.50 x 8 mm.

Liquid 100 parts by weight of ethanol by volume), to which have been added:

10 parts by weight of dimethylcentralite 2 parts by weight of diphenylamine Result After 22 hours at a temperature of 50 C.aHC 815 cal.

EXAMPLE VI Powder As in Example V.

After 36 hours at a temperature of 37 C.--aHC 790 cal.

EXAMPLE VII Powder 13.1% N, to which have been added per parts by weight of dry matter:

1 part by weight of diphenylamine 2 parts by weight of centralite 10 x 10 x 1 mm.

Liquid 100 parts by weight of ethanol which have been added:

3.1 parts by weight of diethylcentralite 6.5 parts by weight of diamylphthalate 1.5 parts by weight of diphenylamine (95% by volume), to

Result After 44 hours at a temperature of 37 C. without a after-treatment-aHC 825 cal.

EXAMPLE VIII Powder As in Example vn.

100 parts by weight of ethanol (95% by volume), to which have been added:

9.8 parts by weight of diamylphthalate 5.2 parts by weight of centralite 1.6 parts by weight of diphenylamine Result After 48 hours at a temperature of 37 C.aHC 752 cal.

EXAMPLE IX Powder Q 13.1% N, to which per 100 parts by weight of dry matter have been added:

1.5 parts by weight of centralite 1.5 parts by weight of diphenylamine 1 part by weight of flame damping salt 330/0.50 x 8 mm.

Liquid 100 parts by weight of ethanol (95% by volume), to which have been added:

10.5 parts by weight of diamylphthalate 4.35 parts by weight of centralite 2.5 parts by weight of diphenylamine Result At a temperature of 37 C.:

After 42 hours--aHC 769 cal. After 48 hoursaHC 725 cal. After 56 hoursaHC 690 cal.

EXAMPLE X Powder 13.1% N, to which per 100 parts by weight of dry matter have been added:

1 part by weight of diphenylamine 1 part by weight of flame damping salt Single perforated cylinder type grain: 3 x 0.40 x 8 mm., wall thickness when dry 0.75 mm. aHC 950 cal.

Liquid 100 parts by weight of ethanol (93% by volume), to

which .have been added:

10.5 parts by weight of diamylphthalate 4.5 parts by weight of diethylcentralite 2.5 parts by weight of diphenylamine Result After 26 hours at a temperature of 49 C.aHC 764 cal.

After 37 hours at a temperature of 37 C.aHC 753 cal. i

After 22 hours at a temperature of 49 C., followed by 6 hours at 37 C.aHC 750 cal.

EXAMPLE XI Powder As in Example X. Single perforated grain: 3/ 0.50 x 8 mm.

Liquid 100 parts by weight of ethanol (93% by volume), to which have been added:

10 parts by weight of diethylcentralite parts by weight of dinitrotoluene 2 parts by weight of diphenylamine Result After 26 hours at a temperature of 45 C.aHC 71s cal.

ddobjriai After 4 hours at a temperature of 37 C.aHC 878 Ads? 6 hours at a temperature of 37 C.aHC s43 Aflgr 8 hours at a temperature of 37 C.aHC 815 m EXAMPLE xm Powder 13.1% N, to which per parts by weight of dry matter have been added:

1 part by Weight of diphenylamine 0.5 part by weight of flame damping salt Single perforated cylinder type grain: 220/ 0.40 x 2 mm. Thickness when dry 0.48 mm.

Liquid 100 parts by weight of ethanol (93% by volume), to which have been added:

10.5 parts by weight of diamylphthalate 4.25 parts by weight of centralite 2.5 parts by weight of diphenylamine Result After 7 hours at a temperature of 39 C.aHC 865 cal After 9 hours at a temperature of 39 C.aHC 841 cal.

EXAMPLE XIV Powder 13.1% N, to which per 100 parts by weight of dry matter have been added:

1.25 parts by weight of diphenylamine 1 part by weight of flame damping salt Single perforated cylinder type grain: 290/040 x 8 mm.

Liquid 100 parts by weight of ethanol (91.5% by volume), to which have been added: 10.5 parts by weight of diamylphthalate 4.35 parts by weight of diethylcentralite 2.5 parts by weight of diphenylamine Result After 22 hours at 45 C. and after vacuum dryingaHC 780 Cal.

After 24 hours at 37.5 C. and after vacuum dryingaHC 673 cal.

EXAMPLE XV Powder 13.1% N, to which per 100 parts by weight of dry matter have been added:

1.25 parts by weight of diphenylamine 1 part by weight of flame damping salt 2 parts by weight of diethylcentralite 13 390/0.50 x 12 thickness when dry 1.05 mm.

Liquid- 100 parts by weight of ethanol (91% by volume), to which have been added:

10.5 parts by weight of diamylphthalate 4.25 parts by weight of diethylcentralite 2.5 parts by weight of diphenylamine Result After 48 hours at 37 C.--aHC 715 cal.

EXAMPLE XVI Powder 1 13.1% N, to wh1ch per 100 parts by weight of dry 5 matter have been added:

1.25 parts by weight of diphenylamine 1 part by weight of flame damping salt 2 parts by weight of diethylcentralite Dimensions-W150 x 15 mm. thickness when dry 1.70 mm.

Liquid 100 parts by weight of ethanol (91% by volume), to which have been added:

10.5 parts by weight of diamylphthalate 4.25 parts by weight of diethylcentralite 2.5 parts by weight of diphenylamine Result After 56 hours at 37 C.aHC 760 cal.

EXAMPLE XVII Powder As in Example XVI, but dimensions: 9.50/3 x 20 mm.-thickness when dry 2.10 mm.

Liquid As in Example XVI.

volume of ethanol and 5% by volume of water to which has been added:

10.5 parts by weight of dibutylphthalate 4.25 parts by weight of diethylcentralite 2.5 parts by weight of diphenylamine Immersion time 29 hours at 37.5 centigrade-aHC 787 cal. aHC of the outermost portion about 400 cal.

EXAMPLE XIX Powder Identical to Example 11.

Liquid 65 100 parts by weight of alcohol containing 95% by volume of ethanol and 5% by volume of water to which have been added:

14 parts by weight of diamylphthalate 2.5 parts by weight of diphenylamine Immersion time 27 hours at C.aHC 792 cal. aI-IC of the outermost portion about 390 cal.

14 EXAMPLE XX Powder 7 3.

Liquid As in Example XIX to which has been added:

15 parts by weight of dibutylphthalate 2.5 parts by weight of diphenylamine Immersion time 25 hours at 42 C.aHC 784 cal. aHC of the outermost portion about 415 cal.

Identical to Example EXAMPLE XXI Powder As in Example X.

Liquid 100 parts by weight of alcohol containing 93% ethanol by volume and 7% water by volume to which have been added:

10.5 parts by weight of dibutylphthalate 4.5 parts by weight of dinitrotoluene Immersion time 26 hours at 43 C.aHC 796 cal. EXAMPLE XXII Powder As in Example 1.

Liquid 100 parts by weight of alcohol containing 91% by volume of ethanol to which has been added:

8 parts by weight of diphenylphthalate 2.25 parts by weight of methyl-ethyl centralite 2.5 parts by weight of diphenylamine Immersion time 30 hours at 39 C.aHC 807 cal.

EXAMPLE XXIII Powder As Example 11.

Liquid 100 parts by weight of alcohol containing 91% ethanol by volume to which have been added:

10.5 parts by weight of diamylphthalate 4.25 parts by weight of methyl-ethyl centralite 2.5 parts by weight of diphenylamine Immersion time 30 hours at 37.5 C.--aHC 793 cal.

aHC of the outermost portion about 390 cal.

What is claimed is:

1. A method of imparting progressive burning properties to molded nitrocellulose gun powder which comprises entirely submerging the molded nitrocellulose gun powder in a solution consisting of ethanol, which ethanol contains -100% by volume of alcohol, and about 10-21% of at least one ethanol-soluble phlegmatizing agent at a temperature of 35 to 50 C. for 7 to 48 hours for nitrocellulose having a wall thickness of 0.75 mm., and for other wall thicknesses for a duration proportional to the square of the ratio of 0.75 to said other thicknesses.

2. A method according to claim 1 wherein another alcohol is added to the ethanol.

3. A method according to claim 1 wherein the solution contains 92.5% alcohol and, for each parts by weight of aqueous ethanol, 10.5 parts diamylphthalate, 4.25 parts ethylcentralite and 2.5 parts diphenylamine, at 37.5 C. for 37 hours for nitrocellulose having a wall thickness of 0.75 mm.

4. A method according to claim 1 wherein the solution contains 91% alcohol and, for each 100 parts by weight 1 of aqueous ethanol, 10.5 parts diamylphthalate, 4.25 parts diethylcentralite and 2.5 parts diphenylamine, at 37 C. for 56 hours for nitrocellulose with 13.1% N and, for each 100 parts by weight' of dry matter, 1.25 parts diphenylamine, 1 part flame damping salt and 2 parts diethylcentralite, and having a wall thickness of 1.7 mm. 5. A product manufactured by the method claimed in claim 1.

6 References Cited in the file of this patent UNITED STATES PATENTS Wagner Aug. 29, 1933 Olsen Jan. 28, 1936 Troxler Feb. 27, 1945 Herzog Feb. 5, 1946 Gallaghan Dec. 7, 1954 

1. A METHOD OF IMPARTING PROGRESSIVE BURNING PROPERTIES TO MOLDED NITROCELLULOSE GUN POWDER WHICH COMPRISES ENTIRELY SUBMERGING THE MOLDED NITROCELLULOSE GUN POWDER IN A SOLUTION CONSISTING OF ETHANOL, WHICH ETHANOL CONTAINS 80-100% BY VOLUME OF ALCOHOL, AND ABOUT 10-12% OF AT LEAST ONE ETHANOL-SOLUBLE PHLEGMATIZING AGENT AT A TEMPERATURE OF 35 TO 50*C. FOR 7 TO 48 HOURS FOR NITROCELLULOSE HAVING A WALL THICKNESS OF 0.75MM., AND FOR OTHER WALL THICKNESSES FOR A DURATION PROPORTIONAL TO THE SQUARE OF THE RATIO OF 0.75 TO SAID OTHER THICKNESSES. 